Fix issue #643: Optimize noqa() with an lru_cache for Python 3.2+. (#644)
Fix issue #643: Optimize noqa() with an lru_cache for Python 3.2+. (#644)

Had to catch a "No signature found for builtin <built-in method
search of _sre.SRE_Pattern object at 0x...>" in 3.4:

In python3.4 the search was not detected as a function, now that it's
wrapped in an lru_cache it is, yet it still has no signature (it has
in 3.5+).
PyCQA/pep8